Conventional Stirling engines for driving ancillary devices are described in JP 64-75865 A and JP 2002-266701 A. The Stirling engine disclosed in JP 2002-266701 A uses heat of reaction generated by a catalytic converter placed in the exhaust system of an internal combustion engine, namely, an automotive power unit, for exhaust emission control as a heat source. Mechanical energy generated by the Stirling engine is used for driving a generator and automotive auxiliary machines. Engine speed of the Stirling engine due to changes in load or the atmospheric condition can be regulated by application of the magnetic field of the generator to control the engine speed of the Stirling engine.
Although the Stirling engine mentioned in JP 64-75865 A uses the heat of a combustion gas produced by a combustor included in the Stirling engine for heating the working gas, nothing is taken into consideration about coupling the brake horsepower of the Stirling engine to the brake horsepower of the internal combustion engine to a common drivetrain to offset load for reducing the fuel consumption of the internal combustion engine. Nor is it taken into consideration of regulating the speed of the Stirling engine by regulation of fuel consumption of the internal combustion engine and further by applying an exhaust brake on the internal combustion engine to transfer the compressive load of the internal combustion engine to the Stirling engine.
The present invention couples the brake horsepower generated by the internal combustion engine and the brake horsepower generated by the Stirling engine to a common drivetrain to reduce fuel consumption of the internal combustion engine with regulation of the speed of the Stirling engine by regulation of the amount of fuel delivered to the internal combustion engine and by transfer of compressive load generated by exhaust brake of the internal combustion engine to the Stirling engine.